(1) Field of the Invention
The present invention relates to a system, method and computer program product for navigating in a virtual environment (VE). More specifically, the present invention relates to navigating large distances in a VE, without becoming disoriented and without becoming cybersick due to exposure to excessive amounts of optical flow.
(2) Description of Related Art
Navigating large distances in a VE provides discomfort to a user. Currently, two commonly used navigation methods are jumping and flying, both are problematic. When jumping, a user often becomes disoriented. While flying preserves the user's orientation, flying exposes the user to optical flow. Optical flow may be defined as the instantaneous velocity of the brightness pattern of an image. It is widely believed that this optical flow can result in the perception of illusory motion, called “vection.” Further, vection is one cause of cybersickenss. While the mechanism by which vection causes cybersickness is not understood, it is generally believed that vection contributes to cybersickness due to visual-vestibular sensory conflict. Experiments by Sharkey and McCauley, in “The effect of global visual flow on simulator sickness,” in Proceedings of the AIAA/AHS Flight Simulation Technologies Conference, American Institute of Aeronautics and Astronautics, Washington, D.C. 1999, pp. 496-504, showed that higher optical flow rates resulted in significantly higher levels of cybersickness in users.
Optical flow may be defined as the instantaneous velocity of the brightness pattern of an image. Given an image I, the optical flow constraint equation may be written as:
      -                  δ        ⁢                                  ⁢        I                    δ        ⁢                                  ⁢        t              =                    (                              δ            ⁢                                                  ⁢            I                                δ            ⁢                                                  ⁢            x                          )            ⁢      u        +                  (                              δ            ⁢                                                  ⁢            I                                δ            ⁢                                                  ⁢            y                          )            ⁢                          ⁢      v      where x and y are the image coordinates, u and v are the horizontal and vertical components of optical flow and t=time, which was described in G. Schunck, “The Motion Constraint Equation of Optical Flow,” in Proceedings of the International Conference on Pattern Recognition, Montreal, Ontario, Canada 1984, p. 20-22. One skilled in the art will appreciate that optical flow may be computed using a variety of techniques, typically by assuming smoothness constraints in the image.
As the magnitude of the optical flow increases, so does the tendency to induce cybersickness, leading to the general approach of minimization of image optical flow to reduce cybersickness. What is needed is a system and method that allows users to move great distances within a VE without becoming disoriented or cybersick. What is needed is a system and method for minimizing optical flow provided to a user.